The invention is applicable primarily to the field of directional or deviated drilling. More in particular, the invention is, therefore, also applicable for use with downhole motors as used in such techniques. These fields, that is, directional drilling and downhole motors, are well developed each in its own right, and thus form part of the invention as to its application, but not part of the invention per se.
More specifically, the present invention concerns a drill string member which makes the bends from the beginning of the well which is vertical, to the horizontal or highly deviated portions thereof. There are known prior art drill members and techniques for accomplishing this, but all of these techniques have numerous disadvantages which are overcome by the present invention. Among the disadvantages are that it has not been known heretofore to make such bends on relatively short radii without using highly specialized and expensive equipment. Conventional drilling and deviated drilling both depend upon lengthening the drill string by adding joints of pipe at the surface. Because of the greatly increased stresses on the drill pipe in directional drilling tending to shorten its life, such bends in prior art drilling techniques have always been made on relatively long radii producing relatively gentle bends. These bends are "expensive" in terms of drilling time and equipment, are not easy to control, and have many other disadvantages well known to those skilled in these arts.
Thus, the present invention provides a relatively limber drill string member particularly adapted for use with but not limited to down hole motors and with measurement while drilling (MWD) techniques. The invention permits the maximum utilization of the advantages of directional drilling and MWD techniques in a highly efficient manner, at relatively low cost, permits making the bends in the borehole on very short radii, while at the same time overcoming all of the disadvantages of the prior art.